Actually North Korea could wipe out America very easily which is why your politicians were so scared ,now you want to know how? very simple. North Korea has 1000s of miles of tunnels underground which is obviously a preemptive defence.

Kim Jong Un has very advanced missiles do not believe the news he is a serious threat, he could easily fire every single missile at America in which your anti ballistics can only stop 50% of missiles (tests have been done) and then you fire back except North Korea will be underground by this time. And most Americans will feel the wrath of Kim while Korea will be relatively safe because of being underground you can fire as many missiles as you want they are SAFE.

Do not underestimate your opponent, and I have a feeling this is gonna happen soon.